Tension Stiffening and Cracking of Steel Fiber-Reinforced Concrete

Fiber-reinforced concrete used in structural applications requires characteristic material properties that can be easily incorporated into existing design procedures. This paper investigates the postcracking response of reinforced concrete tension members made with both plain and steel fiber-reinforced concrete (SFRC). Loading was either monotonic or cyclic, and shrinkage effects are included in analysis of the member response. Tension-stiffening results are used to determine the average tensile response of concrete after cracking, and an expression is developed to predict this smeared behavior as a material property for cracked SFRC, as well as to estimate crack spacings. Specimens with steel fibers exhibited increased tension stiffening and smaller crack spacings, which both contributed to a reduction in crack widths. The postcracking tensile strength of fiber concrete at the cracks is the determining factor affecting behavior and is a fundamental material property used to predict tension stiffening and crack behavior for conventionally reinforced SFRC. The uniaxial strength of SFRC immediately after cracking governs serviceability behavior, while the postcracking strength at larger deformations governs strength design and is responsible for tension stiffening after yielding of the reinforcement. Cyclic loading did not have a significant effect on either tension stiffening or crack width control for the specimens tested.